1. Field of the Invention
The present invention relates to a COF packaging structure and related method, and more particularly, to a COF packaging structure considering thermal dissipation and TCP assembly process by respectively disposing two metal foils each with a designated pattern on two surfaces of a substrate of the COF packaging structure and a related method.
2. Description of the Prior Art
In the past, driver ICs of TFT-LCD panels must carefully consider the tape carrier package (TCP). However, because of lower cost, fine pitch, flexibility, and capable of carrying passive elements, the ratio of the driver ICs adopting chip-on-glass (COG) packaging and chip-on-film (COF) packaging in large TFT-LCD panels has increased. Therefore, the market requirements for driver ICs with COG and COF packaging are becoming more demanding.
Due to requirements for higher frame frequency, driving voltage, and higher display channel of the TFT-LCD panels, a driver IC's thermal dissipation capability is becoming more and more critical. One solution for enhancing the thermal dissipation capability is a COF packaging structure is with two metal layers. Please refer to FIG. 1 together with FIG. 2. FIG. 1 is a diagram of COF packaging structures according to the prior art, and FIG. 2 is a diagram showing thermal dissipation of the COF packaging structures shown in FIG. 1. As shown in 1A, a COF packaging structure 100 includes a substrate 110, a first metal foil 120, and a solder resist layer 130. The substrate 110 is composed of polyimide (PI) film, and the first metal foil 120 is disposed on a first surface 112 of the substrate 110. The solder resist layer 130 is covered on the first metal foil 120. In addition, a driver IC 140 is bonded on the COF packaging structure 100, wherein bumps 142 of the driver IC 140 are bonded on a first designated pattern 122 of the first metal foil 120. As shown in 1B, a COF packaging structure 150 is similar to the COF packaging structure 100, and the difference between them is that the COF packaging structure 150 further includes a second metal foil 160 disposed on a second surface 114 opposite to the first surface 112 of the substrate 110. As shown in FIG. 2, the temperature of the driver IC 140 with the COF packaging structure 150 is much lower than that with the COF packaging structure 100. Therefore, the thermal dissipation capability of the COF packaging structure 150 can be improved by adding the second metal foil 160.
Although the thermal dissipation capability of the COF packaging structure 150 can be improved by adding the second metal foil 160, however, it is also necessary to consider its feasibility in the TCP assembly process. As shown in 1B, because the second metal foil 160 is fully covered on the second surface 114 of the substrate 110, a conventional IL (inner lead) bonder with only one charge coupled device (CCD) is not suitable for the COF packaging structure 150 due to the CCD being unable to see through the COF packaging structure 150. As a result, a new IL bonder with two CCDs would be necessary for the COF packaging structure 150, resulting in higher costs during the TCP assembly process.